This invention relates to appartus for processing liquid radioactive waste materials, and more particularly, to apparatus for processing such materials for shipment and storage in solid form.
There are many methods of disposing of radioactive waste materials. One method is to mix the radioactive waste with cement or the like, let the mixture harden in one or more containers, and ship the containers to a storage site.
Solid radioactive waste materials may be too highly radioactive to be shipped safely. For example, waste fuel from nuclear power plants may have radiation levels of between about 500 R/hr and about 1,000 R/hr. Such levels are very dangerous.
Radiation levels of about 100 mR/hr are considered safe for transport. In order to reduce the radioactivity of highly radioactive solid waste materials, the materials may be dissolved and diluted to produce a waste solution having a reduced concentration of radiation. A liquid containing nitric acid is desirable for producing such solutions because it dissolves commonly encountered radioactive waste materials.
In order to fix a solution containing radioactive waste materials in solid form, the solution must be mixed with cement or some other fixing agent in a suitable container. Desired levels of radiation may be achieved by controlling the ratio of the waste materials to fixant. After the mixture hardens, cures and is dehydrated, the container may be transported to an appropriate site for storage, after packaging in proper containers.
Under normal circumstances, the volumetric ratio of waste solution to fixant is substantially less than one. The ratio might be as low as 0.02. In such situations, it is not uncommon to put the fixing agent into the container in slurry form first, and slowly meter the solution into the container while constantly blending the mixture. However, the mixing process creates radioactive vapors which could be very harmful if they are permitted to escape into a work area or into the atmosphere. Mixing may be performed in a sealed chamber to contain such vapors, but the vapors must be substantially eliminated before the chamber is unsealed to remove the containers. Thus, there is a need for apparatus for fixing radioactive waste in solid form which controls vapors created by the mixing and setting process.
The liquid radioactive waste materials and fixing agent should be blended to produce a homogeneous mixture in which the waste materials are evenly dispersed throughout the container. This may be accomplished by inserting rotatable blades into the mixture, rotating the blades for a suitable length of time, and removing the blades before the mixture hardens. If the top of the container has an opening of reduced size relative to the circumference of the container, the size of the blades must be reduced to allow it to fit through the opening. As a result, such blades do not extend to the wall of the container, and thorough blending of the mixture is difficult to achieve. Thus, there is a need for mixing blades which fit through an opening in a container, the opening being smaller than the outer circumference of the container, and the blades being capable of adjustment inside the container so that the blades pass adjacent to the inside surface of the container wall.
Accordingly, one object of this invention is to provide new and improved apparatus for processing radioactive waste materials.
Another object is to provide new and improved apparatus for processing radioactive waste materials for shipment and storage in solid form.
Still another object is to provide new and improved apparatus for controlling radioactive vapors in chambers containing radioactive waste materials.
Yet another object is to provide new and improved apparatus for inserting mixing blades through an opening in a container, the opening being smaller than the outer circumference of the container, and adjusting the blades and the container so that the blades extend adjacent to the inside of the wall of the container.